1. Field of the Invention
This invention relates to apparatus for, and a method of, measuring the concentricity of the profiles, in transverse section, of a light-transmissive core and a light-transmissive cladding around the core, and is particularly useful in the quality control of optical fibre preform manufacture.
2. Description of Related Art
The measurement of the core reference circle centre to cladding reference circle centre on a fibre preform is important both for production control and to prevent the pulling of fibre which is out of the required specification. Existing methods are excessively slow and require of operator intervention.